Feature channelrouter (sparse matrix, other version of #656)

CHANGELOG.md

@@ -12,6 +12,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 - Adds a function to write a `Source` to a `wav` file, see `output_to_wav`.
 - Output audio stream buffer size can now be adjusted.
+- A `ChannelRouterSource` that can mix, re-order and extract channels from a 
+  multi-channel source.
+    - Several `Source` trait helper functions including `extract_channel`, 
+      `extract_channels`, `mono`, `mono_to_stereo`, and `downmix_51`.
+    - A `ChannelRouterController` type to modify the `ChannelRouterSource` 
+      across thread boundaries.
 - Sources for directly generating square waves, triangle waves, square waves, and
   sawtooths have been added.
 - An interface for defining `SignalGenerator` patterns with an `fn`, see

Cargo.toml

@@ -88,6 +88,10 @@ required-features = ["symphonia-isomp4", "symphonia-aac"]
 name = "noise_generator"
 required-features = ["noise"]
 
+[[example]]
+name = "channel_routing"
+
 [[example]]
 name = "into_file"
 required-features = ["wav", "mp3"]
+

examples/channel_routing.rs

@@ -0,0 +1,45 @@
+//! Channel router example
+
+use std::io::Read;
+use std::{error::Error, io};
+
+fn main() -> Result<(), Box<dyn Error>> {
+    use rodio::source::{Function, SignalGenerator, Source};
+
+    let stream_handle = rodio::OutputStreamBuilder::open_default_stream()?;
+
+    let sample_rate: u32 = 48000;
+
+    let (controller, router) = SignalGenerator::new(sample_rate, 440.0, Function::Triangle)
+        .amplify(0.1)
+        .channel_router(2, &vec![]);
+
+    println!("Control left and right levels separately:");
+    println!("q: left+\na: left-\nw: right+\ns: right-\nx: quit");
+
+    stream_handle.mixer().add(router);
+
+    let (mut left_level, mut right_level) = (0.5f32, 0.5f32);
+    controller.set_map(&vec![(0, 0, left_level), (0, 1, right_level)])?;
+    println!("Left: {left_level:.04}, Right: {right_level:.04}");
+
+    let bytes = io::stdin().bytes();
+    for chr in bytes {
+        match chr.unwrap() {
+            b'q' => left_level += 0.1,
+            b'a' => left_level -= 0.1,
+            b'w' => right_level += 0.1,
+            b's' => right_level -= 0.1,
+            b'x' => break,
+            b'\n' => {
+                left_level = left_level.clamp(0.0, 1.0);
+                right_level = right_level.clamp(0.0, 1.0);
+                controller.set_map(&vec![(0, 0, left_level), (0, 1, right_level)])?;
+                println!("Left: {left_level:.04}, Right: {right_level:.04}");
+            }
+            _ => continue,
+        }
+    }
+
+    Ok(())
+}

src/mixer.rs

@@ -7,7 +7,7 @@ use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::{Arc, Mutex};
 use std::time::Duration;
 
-/// Builds a new mixer.
+/// Builds a new mixer that sums corresponding channels from incoming streams.
 ///
 /// You can choose the characteristics of the output thanks to this constructor. All the sounds
 /// added to the mixer will be converted to these values.
@@ -116,7 +116,7 @@ where
         // let mut encounterd_err = None;
         //
         // for source in &mut self.current_sources {
-        //     let pos = /* source.playback_pos() */ todo!();
+        //     let pos = /* source.playback_pos() */
         //     if let Err(e) = source.try_seek(pos) {
         //         encounterd_err = Some(e);
         //         break;